For the back the pattern is exactly the same, but you will need to divide for the button placket.
Repeat all instructions for the back. Remember though, that as you’re working in a button placket, you will split your work near the back neck, to accommodate the button placket.
Repeat for the second armhole as well.
So what we will do here is work a fsc chain, and then work the pattern first on one side, and then swing around and work the same pattern on the other side of the same fsc chain.